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Does SI request RACH happens using contention free or contention based in NR?

+1 vote
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Does SI request RACH happens using contention free or contention based in NR?
posted Mar 7, 2018 by Jaganathan

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2 Answers

+1 vote

As I know, In the contention-free mode, the eNB can uniquely identify the UE by a received preamble sequence, due to the fact
that the preamble to be used has been communicated to the UE in advance. Such a scenario is possible in certain cases,
e.g., during a handover between two eNBs.
In on demand SI request RACH, RACH-ConfigDedicated mode used & it is used for handover to the cell. So I think in this case contention-free RA procedure will use.
Waiting for other expert comment !!

answer Mar 7, 2018 by Mohit Mohan
0 votes

►The Random Access Procedure is used for four cases:
• Initial access from disconnected state (RRC_IDLE)
• Handover requiring random access procedure
• DL or UL data arrival during RRC_CONNECTED after UL PHY has
lost synchronization (possibly due to power save operation)
• UL data arrival when are no dedicated scheduling request channels
available
►There are two forms of the Random Access Procedure
• Contention based (applicable to all four events)
• Non-contention based (applicable to only handover and DL data
arrival)

answer Jan 30 by Thierry Bodog
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0 votes

weather it is RRCConnection request or direct NAS message as ULInfotransfer?

+1 vote

If HO fails the UE will initiate contention based reestablishment and connect to some ENB, But target ENB have provided the contention free Rach preamble , at failure case how long ENB will hold this preamble because it has to release for other UE?

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